August 2010
Volume 10, Issue 7
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2010
Perceiving and controlling actions: Visually perceived distances map onto different forms of throwing as a function of the ball's weight and constraints on throwing actions
Author Affiliations
  • John Rieser
    Vanderbilt University
  • Aysu Erdemir
    Vanderbilt University
  • Gayathri Narasimham
    Vanderbilt University
  • Joseph Lappin
    Vanderbilt University
  • Herbert Pick
    University of Minnesota
Journal of Vision August 2010, Vol.10, 1074. doi:10.1167/10.7.1074
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      John Rieser, Aysu Erdemir, Gayathri Narasimham, Joseph Lappin, Herbert Pick; Perceiving and controlling actions: Visually perceived distances map onto different forms of throwing as a function of the ball's weight and constraints on throwing actions. Journal of Vision 2010;10(7):1074. doi: 10.1167/10.7.1074.

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Abstract

People control their own actions and judge the results of other's actions from the action's kinematics. We study the psychophysics when children & adults vary the forms of their throwing to accommodate for varying target distances, ball weights, and constraints on whether they can rotate elbow, shoulder, waist or step forward. People control the forms of their throwing to fit with the different ranges of visually perceived distance. For a 1m target they swing from the elbow alone, to a 5m target from elbow & shoulder, and so forth out to 30m targets. They know how many of the available degrees of freedom in the throwing action are needed to generate enough force to reach the target's vicinity. In Study 1 4-6 year olds & adults were video taped while throwing to visual targets ranging from 1-30m. Throw dynamics/kinematics were constrained by varying the ball's weight, wrist weights, & constraining movements across some swing points. How would people adapt, we ask, when tossing to nearby targets with their elbow constrained? How would they adapt when tossing to far away target without stepping or waist rotation? Study 2 was aimed at investigating the accuracy with which 4-6 year olds and adults can judge the thrown distance by observing the kinematics of others' throws. People viewed videotapes of throws up to the instant of release; they judged the throw's distance & trajectory from the hand/ball's velocity. Weber fractions were used to describe the thrown distances across target distances. Children & adults alike coped with the constraints in sensible ways, always varying the form of throw in ways that let them control the hand/ball's velocity. Finally, children & adults were not accurate at judging the thrown metric distance from videotapes, but were remarkably accurate at rank ordering the thrown distances.

Rieser, J. Erdemir, A. Narasimham, G. Lappin, J. Pick, H. (2010). Perceiving and controlling actions: Visually perceived distances map onto different forms of throwing as a function of the ball's weight and constraints on throwing actions [Abstract]. Journal of Vision, 10(7):1074, 1074a, http://www.journalofvision.org/content/10/7/1074, doi:10.1167/10.7.1074. [CrossRef]
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